The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.
Fabric conditioning compositions can be added in the rinse cycle of the laundering process to soften fabrics and to impart them nice smell. Conventionally, fabric conditioning systems are based on quaternary ammonium compounds, also named as quats, notably cetrimonium chloride, behentrimonium chloride, N,N-bis(stearoyl-oxy-ethyl) N,N-dimethyl ammonium chloride, N,N bis(tallowoyl-oxy-ethyl) N,N-dimethyl ammonium chloride, N,N bis(stearoyl-oxy-ethyl) N-(2-hydroxyethyl)N-methyl ammonium methylsulfate or 1,2-di(stearoyl-oxy)-3-trimethyl ammoniumpropane chloride. Advantageously, ester quats can be used as fabric conditioning actives. Ester quats are bio-degradable and exhibit lower eco toxicity, and therefore, there is a trend in the industry to use ester quats as the fabric conditioning actives.
It is highly desirable that the fabric conditioning compositions can have good conditioning performance combined with excellent stability. Fabric conditioning compositions with poor stability may become unpourable and have inadequate dispensing and dissolving characteristics in rinse water. This is in particular a problem when the fabric conditioning actives are present at high concentrations which may be required for achieving good conditioning performance. One option to solve this problem is to lower the dosage level of the quats in the composition by replacing some of the quats with a cationic polymer, such as a cationic polysaccharide. The art teaches that addition of cationic polymers to fabric conditioning compositions has a variety of benefits. U.S. Pat. No. 6,492,322, Megan et al., discloses fabric softening compositions comprising biodegradable di-ester softening compounds and cationic polymers including polysaccharides, such as gums, starches and certain cationic synthetic polymers.
However, replacing the quats with a cationic polysaccharide in the fabric conditioning compositions will lead to another problem. More specifically, the quats and the cationic polysaccharide, when combined, tend to separate. As a result, compositions comprising such components are no longer homogeneous and segregate into different phases. This is in particular an issue when these compounds are combined in an aqueous composition. This may pose problems to the user upon usage or may affect retailers when placing products on the shelves, without mentioning any associated loss of performance for the softening products.
Thus, it remains a challenge to provide a fabric conditioning composition having excellent softening performance combined with good stability. It remains a challenge to provide a fabric conditioning composition which can have long shelf life and which can remain stable and homogenous for extended time. In particular, it remains a challenge to provide a fabric conditioning composition with good stability without jeopardizing the dispersibility of the composition in aqueous solutions.
Laundry operation in which a fabric conditioning composition is used usually involves washing fabrics with a detergent composition, such as a detergent liquor, removing majority of the detergent composition, and subsequently treating the fabrics with a rinse solution containing the fabric conditioning composition. Such use of the fabric conditioning composition in conjunction with the detergent composition has certain problems. In particular, fabric conditioning actives, which are unusually cationic in nature, may interact with laundry residues carried over to the rinse solution from the washing step. Such laundry residues notably include anionic surfactants which are commonly used in detergent compositions. The interaction between the fabric conditioning actives and the carry-over laundry residues may result in a reduced conditioning effect, such as a reduced softening effect. The interaction may also lead to presence of poorly soluble flocs in the rinse solution which causes troubles to consumers. Such problems are particularly evident when the ratio of detergent to water is high in the washing step which may be required for achieving satisfactory cleaning effects. One way to solve these problems is to rinse and spin the fabrics repeatedly before bringing the fabrics to the rinse solution so as to remove most of the laundry residues. However, this will require high water consumption and prolonged time for the laundry operation.
Thus, aside from the stability problems mentioned above, it also remains a challenge to provide a composition which has excellent fabric softening effects when being used in conjunction with high dosage detergent that is added in the washing step. It remains a challenge to provide a method for rinsing fabrics which allows excellent conditioning effects even in the presence of laundry residues and which is time saving and cost efficient.